1. Field of the Invention
This invention relates to a method for the preparation of a halogen-substituted organic compound by the reaction of an olefin with an organic carbonyl compound which may contain certain other functional groups described hereinbelow. In particular, it relates to the preparation of an oxidatively coupled adduct of an olefin in which an atom of halogen is incorporated into the molecular structure during the reaction.
2. Description of Background Synthesis
U.S. Pat. No. 4,011,239 issued Mar. 8, 1977, of which the present invention is a continuation-in-part, describes a method for oxidatively adducting an olefin with a ketone, an aldehyde, an ester, a nitrile, a nitroparaffin, a sulfoxide, a thiosulfonic acid ester, an alkanesulfonic acid, an alkanesulfinic acid, or a thiol. The reaction whereby the olefin and other component is oxidatively adducted is effected by reacting the two organic components in solution in the presence of a stoichiometric amount of an ion of manganese, cerium, or vanadium in a valence state higher than the lower valence state above the zero valent form of the metal. During the reaction, the ion of manganese, cerium or vanadium, which must be an oxidizing ion in the reaction environment, is reduced to a lower valent form as shown hereinbelow.
In the above-identified U.S. Pat. No. 4,011,239, the adduction reaction is described as proceeding via the free radical .X formed in the reaction between the ketone, aldehyde, etc. and the oxiding ion. The free radical .X in turn reacts with the compound having olefinic unsaturation, i.e. the olefin. The .X radical reacted with the compound have olefinic unsaturation is one selected from the following classes: ##STR1## These free radicals are derived respectively from a symmetrical or an unsymmetrical ketone, an aldehyde, an ester, a nitrile, a nitroparaffin, a symmetrical or unsymmetrical sulfoxide, a thiosulfonic acid ester, an alkanesulfonic acid, an alkanesulfinic acid, and a thiol.
In the free radicals described above, the dangling valences may be satisfied by a wide variety of groups. R is generally an alkyl group. R' is generally a hydrocarbyl or substituted hydrocarbyl group. The method is capable of providing high yields of valuable products containing the moiety ##STR2## where X is one of the radicals just defined.
As a specific example, the reaction sequences and the types of products obtained with the ketone-derived radical ##STR3## are described in the forementioned patent. The sequences are herein repeated in equation form (Equations 1-5), with the olefin designated as R"CH.dbd.CH.sub.2, R" being hydrogen or a hydrocarbyl group. Further, Mn.sup.+++ is used as the metal ion, and manganic acetate as the source of the Mn.sup.+++, ##STR4## as the specific free radical, and acetone as the ketone from which the specific free radical is derived. As shown in equation (1), the ##STR5## free radical is produced when manganic acetate, dissolved in acetic acid, is heated with acetone. According to the reaction of equation (2), the reactive acetylmethyl free radical, ##STR6## adds to the double bond of the olefin, forming the free radical (A). In equation (3), oxidation of free radical intermediate (A) occurs in the presence of manganic acetate to form the cation intermediate (B), with reduction of Mn.sup.+3 to Mn.sup.+2 and formation of an acetate ion. In equation (4), the cation (B) reacts with the acetate ion to form the keto-ester product (P-1), about 90% of the Mn.sup.+3 consumed forming this product. As shown in equation (5), about 10% of the Mn.sup.+3 consumed forms the beta-gamma unsaturated ketone product (P-2) by losing H. If R" is hydrogen, the product (P-1) is 1-acetoxy-pentanone-4, and (P-2) is 1-penten-4-one. It is pointed out that the acetylmethyl free radical is not substantially oxidized by Mn.sup.+3, but the free radical intermediate (A) is readily oxidized, thus providing a case of selective oxidation. In other words, (A) has a lower ionization potential than the acetylmethyl radical. The ion intermediate (B) may react in either of two ways, as shown in equations (4) and (5).
As disclosed in U.S. Pat. No. 4,011,239, certain circumstances may induce products other than (P-1) and (P-2) to form. For example, when R" is a phenyl group, the unsaturated ketone product (P-2) is not obtained; rather, a dihydrofuran product forms instead. Also, when the solvent contains water, thus providing hydroxyl ion, some of the product (P-1) contains a simple hydroxyl substituent in place of the acetate ester group shown. ##STR7##
It is clear from the foregoing description that the overall reaction requires two equivalents of oxidizing ion per mole of product that is formed, i.e. a stoichiometric amount of oxidizing ion of manganese, cerium or vanadium. Actually, in practice, some of the oxidizing ion may be consumed in side reactions, so that somewhat more than the required two equivalents are consumed overall per mole of product. The reaction thus is clearly distinguished from those reactions in which a catalytic amount of metal ion is used.
Another aspect of the adduction reaction is that the functional group of the compound that forms the radical .X is preserved in the adducted product. Thus, reacting an olefin with a ketone forms an adduct which itself is a ketone; with an aldehyde as reactant, an adduct is formed which itself is an aldehyde; and with a diester, an adduct which also is a diester.
The entire contents of U.S. Pat. No. 4,011,239, which describes the background synthesis involved in the present invention, is incorporated herein by reference.